Telemetering system



April 16, 1940. F Q 2,197,636

TELEMETERING SYSTEM Original Filed Jan. 28, 1959 Th Race/var:

76 Receive? Inventor:

Harold T Faus,

by Hi Attorney.

Patented Apr. 16, 1940 UlillTED- STATES PATENT OFFICE TELEMETEBING SYSTEM Harold '1. Fans, Lynn, Mass., assignor to General Electric Company, a corporation of New York Original application January, 1939, Serial No.

Divided and this application April 20, 1939, Serial No. 268,971

2 Claims. -(Cl. 172-239) revolutions may be produced at a receiving sta-' tion in response to rectilinear motion or motion through a small angle at a transmitting station. Other and further objects and advantages will become apparent as the description proceeds. 'I'elemetric systems in which a deflection or a rotation may be-repro'duced at a distance are applicable to the transmission of numerous types of measurements. For example, in electrical tachometers, the movable arm of a sending unit may be operated by a centrifugal device similar to that in a centrifugal tachometer. Remote temperature indication may take place with a bimetallic strip or a Bourdon tube actuating the movable arm of the sending instrument. In liquid level indicators for water, oil, and gasoline tanks, a float would be provided for actuating the movable arm of the transmitting instrument. Similarly the positions of valves, controls, weather vanes, etc., may be remotely indicated by having connections to the movable arm of a transmitting instrument. In conjunction with Venturi tubes or standard orifices and suitable mechanical devices actuated by differential pressure, the movable arm of the transmitting instrument may be operated to indicate at a distance and integrate the flow of fluids.

5 In accordance with my invention in one of its preferred forms, I provide at the transmitting end a toroidal orcircular rheostat and a rotatable diametral arm carrying brushes at the ends through which direct current is supplied to the 40 toroidal rheostat. At the receiving end, a

toroidal winding is provided having a transversely magnized coaxial rotor of high-coercive force magnetic material carrying an indicating pointer. Corresponding points around the periphery of the toroidal rheostat and the toroidal winding are connected by conductors extending between the transmitting and receiving stations.

The invention will be understood more readily from the following detailed description when considered in connection with the accompanying drawing and those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. In the drawing, Fig. l is a circuit diagram representing schematically one form of my invention; Fig. 2 represents a modifled form of transmitting instrument for transmitting straight line indications or for use in converting 60 straight line motion into circular motion; and

Fig. 3 is a diagrammatic representation of rectilinear motion transmitter which I have devised for causing the receiver to make a plurality of revolutions.

Fig. 1 illustrates the'appiication of my in- 5 vention to the remote indication of pressure. A Bourdon tube pressure gage has a movable element l2 connected to a movable arm II of a telemetric transmitting instrument It. The instrument It includes an annular rheostat i5 10 which may conveniently be wound upona toroid or upon an annulus. The movable arm ll carries a pair of contact blades or brushes i6 which are insulated from-each other and which contact at the ends with two diametrically opposite points 15 p in the rheostat IS. The arm It lies along adiameter of the rheostat l5 and is rotatable about the center thereof in response to deflection of the Bourdon tube gage H. A suitable some of direct-current I1 is connected to the brushes or so contacts it.

v At the receiving station, there is a receiving instrument or indicator comprising a fleld or stator winding is and a permanent magnet armature or rotor I9. The winding la is divided into 25 not less than three coils 20, 2i and 22 which, in the arrangement of Fig. 1, are connected in series to form a toroidal .winding with not less than three terminals or taps 23, 24, and 25 at equidistant points around the periphery of the 30 toroidal winding It. The terminals 23, 24, 25, are connected to corresponding terminals 26, 21, and 28, which are connected to points equidistantaround the periphery of the annular rheostat IS.

The armature I! is preferably substantially 35 cylindrical in shape or has a substantially circular cross section conforming in shape to the inner surface of the winding l8 and is substantially coaxial therewith. The armature i9 pose of increasing both the deflection-producing torque and the damping and for adequately shielding the receiver from stray magnetic flelds, I may provide a core 30 for the winding it composed of a magnetic material having a high permeability and low hysteresis, for example, such as a nickel-iron alloy containing approximately78 per cent nickel. The use of lowhysteresis material prevents sluggishness or lag of the armature due to stator losses and contributes to the extremely rapid responsiveness of telemeter systems employing my receiver.

The core may be composed of fiat rings or annular laminations, the axial length of the core 30 being preferably substantially no less than the axial length of the rotor I9. I have found that satisfactory shielding is obtained when the rotor I9 and the core 30 have substantially the same axial length. The core 30 serves the dual purpose of shielding the instrument against external fields and guiding the stator flux to diametrically opposite points of the stator as to cross the air gap diametrically. It will be observed that the rotor l9 conforms substantially in shape to the opening within the annular core 30.

.alloy of iron and six to fifteen per cent aluminum and twenty to thirty per cent nickel, for example. However, for the sake of obtaining increased lightness, reduction in inertia, elimination of the necessity for insulation, and for obtaining maximum efiiciency of utilization of magnet material, I prefer to employ a material such as that described in the copending application of Ralph G." Arey and Harold T. Faus, Serial No. 50,508, filed November 19, 1935. and assigned to the same assignee as the present application. When composed of this material, the rotor consists of a solid unlaminated block of circular cross section which is polarized across a diameter thereof. The material is prepared and magnetized as follows:

Mix together finely powdered magnetite, ferric oxide, and cobaltic oxide in the proportions of 43.6% magnetite, 30.1% ferric oxide, and 26.3% of cobaltic oxide. Mold the mixture in the shape 4 desired under pressure of from three to five tons per square inch. Remove from mold and heat in an atmosphere of nitrogen or air for two or three hours at about 1000 degrees C. and allow to cool. Then reheat to about 520 degrees C. in a special furnace placed in the air gap of a diroot-current electromagnet with afield of about 3000 H. With the field on, lower the temperature to about 300 or 320 degrees C. and hold in the field within this range of temperature for about three-quarters of an hour. Then allow to cool in the field to below degrees C. The material may then be machined or ground to shape, if necessary. An unusual property of this material which I have discovered and which makes it particularly suitable for telemetric receiving is that although it may be magnetized in a given transverse direction while hot it is virtually impossible thereafter to shift the line of magnetization to a different angle without raising the temperature to about 300 degrees. It is believed that the materials described in United States Patents No. 1,997,193 and No. 1,976,230 to Kato et al. will also be useful for the rotor material on some forms of theapparatus although I have found that the sintered oxide material which I have described, produces telemeter receivers with the best performance.

Such material after being magnetized, in addition to being a permanent magnet of exceptionally high coercive force and adequate, although lower, residual induction than some of the common permanent magnet materials, has other remarkable properties. It has a resistance between 600,000 and 1,000,000 ohms per cm. cube and is thus practically an insulator. It is hard and of a gray slate color. It is very light in weight as compared to other magnetic materials, having a specific gravity of approximately onehalf that of ordinary steel. The'coercive force of the material prepared as previously described is between I00 and 1000 oersteds and'has a residual induction of about 2000 lines per square centimeter. The available magnetic energy of the material per unit volume .is approximately 1,000,000 measured in terms of the maximtun value of the product of flux density and field strength in lines per square centimeter or Gausses and in Gilberts per centimeter respectively. Accordingly, the ratio of the magnetic energy per unit volume to the specific gravity or the magnetic energy per unit mass is over 2,000,000 measuring specific gravity in terms of that of steel. Likewise the ratio of residual induction to specific gravity exceeds 4000.

Since the line of polarization is very definite and fixed and does not shift, the scale need not be recalibrated and reset in case the windings should be deenergized and re-energized with the rotor in a different position. As a cylindrical magnet composed of the sintered oxide material behaves just as if it were a thin line permanent magnet, the position assumed by the pointer is very definite and the exact position may be relied upon as an accurate indication of the measurement transmitted.

I prefer to make the diameter of the rotor about twice its axial thickness as this appears to represent approximately the most efficient design of permanent magnet for the shape and material used. In order to give a clearer understanding of this statement, it may be said that the most eflicient design of a cobalt steel bar magnet isone having a ratio of length to diameter of bar of about 8 to 1. Due to the higher coercive force and lower residual induction of the sintered oxide material used in my rotor, the most efficient design of a bar magnet made thereof is one where the ratio of length to diameter is about 2 to 1. It thus becomes evident that the solid cylindrical rotor of sintered oxide having a diameter about twice its axial thickness and polarized across a diameter thereof is an emcient permanent magnet which lends itself much more readily to a compact design with minimum leakage than would a rotor which cannot efficiently occupy but a small fraction of the total space included within the annular stator. It will be seen that in the arrangement of Fig. 1, the total length of air gap between the rotor l9 and the core 30 is more than one-fourth, in fact, nearly one-half the diameter of the rotor l9. Since the core is composed of permeable material relatively little magnetomotive force is required to pass flux through it, and the drop in magnetic potential occurs practically entirely across the air gap. The magnetic energy and residual magnetization of the sintered oxide rotor is so high that a minimum flux density in the air gap of 250 Gausses due to the rotor may readily be maintained thus providing very powerful and positive damping action as well as high torque.

The manner of operation of the apparatus will be apparent from the consideration of the fact that, as the arm I! is rotated, the polarities and relative magnitudes of the voltage drops in the three sectors of the rheostat 15 will be varied. The voltages applied to the coils 20, 2|, and 22 will produce fluxes in the core 30 which combine to produce a resultant magnetomotive force in a of the movable arm l2. For example, in the position shown, the voltages applied to'the coils will increase whereas that applied to the coil 2| will decrease, causing the direction ot'the resultant flux in the receiver to rotate with the arm l2.

Inasmuch as the connections of the transmitter and receiver are symmetrical with respect to a transverse line between them, it will be apparent that the angular positions the arm l2 and the pointer u will also be symmetrical and the pointer 2| will rotate in a clockwise direction as the arm |2 rotates in a counterclockwise direction and -vice versa. The angular stator core 28, it will be observed, is smooth and toothless so that the flux paths vary smoothly as the armature isrotated, and consequently the rotation takes place smoothly without jerkiness or jumping. Since the taps and windings on the transmitter and receiver are radially symmetrical with respect to their respective axes, the rate of rotation of the pointer 2| is substantially uniform throughout its path of rotation. The angular direction of the diametrical stator flux varies smoothly and precisely as the arm I2. is rotated to vary the current ratios andpolarities in the stator coils, and the rotor flux is unaii'ected by rotation since the reluctance of its magnetic circuit, primarily the air gap reluctance, is the same for all angular positions.

In connection with the transmission of certain types of indications, such as the height of a float.

I I in a liquid level indicator, it is more convenient to employ a rectilinear motion transmitter arranged tohave its contacts move in a straight line of the type illustrated in Fig; 2 in which the resistor I! of Fig. 1 is replaced by a special rheostat including two straight resistors 22 and 24 tapped at suitable points for connection to the terminals 26, 21, and 28 from which suitable conductors .lead to corresponding receiver terminals 24, 22,

and 22, as in the arrangement of Flg. 1. In the arrangement of Fig. 2, the ends of the resistor 22 are connected together and the ends of the resistor 24 are connected to the midpoint 22 of the resistor 22. For a substantiallyuniform scale distribution. the arrangement of Fig. 2 has the termlnal 22 connected at the lower end 01' the resistor 24, the terminal 22 connected one-third of the way up on resistor 24, and the terminal 21 connected two-thirds oi the way up on the resistor 24. A tap one-sixth oi the way up on. resistor 22 is likewise connected to the terminal 21 and a. tap iive-sixths of the way up on resistor 22 is likewise connected to the terminal 26. It will be understood, however, that the location of the taps may be varied when it is desired to change the scale distribution.

'Ihe movable arm l2, in this case adapted for straight line up and down motion, carries contacts I6 connected to a source of direct current l1 and the contacts are adapted to slide along the resistors '22 and 24 corresponding to the action in Fig.1. As the contacts l6 slide up and down the resistors 22 and 24, the polarities oi the voltageapplied between the terminals 22, 21, and 22 will vary in a manner analogous to that explained in connection with Fig. 1. I

If it is assumed that the sliding arm 12' is initially at the lowermost position and the contacts It at the lower ends oi! the resistors 22 and 24, the potential of the terminal 28 will have its maximum negative value since the right-hand one of the contactors i6 is connected to the negative terminal of the source I1. As the sliding arm moves towards the halt-way position, the potential .of .the terminal 28 becomes less negative and more positive until the arm l2 reaches the half -way position in which the left-hand contact I8 is at the mid tap 26. In this position, the left-hand or positive terminal of the source I1 is connected through the conductors 21 and 28 to the terminal 28, the potential of which accordingly has its maximum positive value. Then, as

thearm l2 moves toward the top, the terminal 28 becomes less positive and more negative until, with the arm |2' in the uppermost position, the terminal 28 is again at the maximum negative potential since the right-hand or negative terminal of the source I1 is now connected through the conductor 28 directly to the terminal 28. The potential of the terminal 28 has thus completed a cycle similar to that of a sine wave but tending to be triangular in shape.

The terminals 28 and 21, which are at the onethird and two-thirds points from the lower end of the resistor 24, go through similar variations of potential but, at times when the contactor is respectively one-third and two-thirds of the way toward the upper end of. the resistor 24. Inasmuch as the terminal 22 goes through a complete voltage cycle when the contactor moves from the lower end to the upper end of the resistor 24, this movement corresponds to 360 electrical degrees. The terminal 22 goes through similar potential variations one-third of the distance later and this, therefore, corresponds to 120 electrical .degrees later. Similarly, terminal '21 goes through its potential variations. 240 degrees later than the terminal 22. The three terminals 28, 28, and 21, therefore, behave like a three-phase system and. when connected to the receiver or indicator of Fig. 1, produce rotation of the armature. I2. It is thus apparent that the motion of the arm I2 the full length of the resistors 22 and 24 is converted into a complete rotation of the pointer 2| I have devised a transmitter for producing any desired number of revolutions of the receiver rotor in response to a given degree of motion of the transmitter mechanism. In the arrangement of Fig. 3 there are two resistors 4| and 42 and a pair of brushes l8 carried by mechanism, not shown, designed to move in a straight line along the resistors 4| and 42 in response to a motion which is to be indicated at a distance. Each resistor has its ends connected together. The resistors are divided into a plurality of equal-resistance parts-or divisions by taps and cross connections between the taps of the two resistors are made. The number of parts into which the resistors are divided is the product of the number of revolutions of the receiver rotor to be produced and v the number of conductors connected between the transmitter and the receiver.

design is for producing three revolutions of the rotor i9 in response to movement of the brushes the full length of the resistors 4| and 42, and three leads 43 are run to the receiver as in Fig. 1. Accordingly, the resistors 4| and 42 are each divided into nine parts. In the case of the receiver 42 the first tap or connection is at the end of the resistor and the remaining taps are spaced along the resistor at distancesapart, each representing one-ninth of the resistance of the resistor. In the case of the resistor 4|, however, the first tap or connection is at a point spaced at a distance from the end of the resistor representing one-eighteenth of the resistance thereof. The remaining taps are spaced along the resistor at distances apart each representing oneninth of the resistance of the resistor so that the two end portions of the resistor 4| together represent one of the nine parts into which the resistor 4| is divided. Each tap of each resistor is connected to taps of the'same resistor spaced away along the resistor one-third the length thereof and is also connected to taps of the other resistor spaced one-sixth resistor length away, i. e., spaced away the length of one and one-half resistor parts or divisions. For identification the taps of the resistor 42 are numbered 1 to 10 inclusive, and the taps of the resistor 4| are lettered A to I, inclusive. Connections are made between taps i, B, i, E, l, H and I0, between taps 2,0, 5, l 8 and Ifand between taps A, 3, D, 6, G and 9. Any three adjacent taps of either resistor such as the taps l, 2 and 3 are connected to conductors such as conductors 43 leading to the receiver, e. g., to the terminals 23, 24 and 25 of Fig. 1. A separate connection between the ends or the resistor 42 is not required since the first tap i is at the end of the resistor and the cross connections from this tap form a conductive path to the last tap H) at the lower end of the resistor 42. The connection between the ends of the resistor 4| is desirable, particularly where the full length of the resistor is to be utilized and the brushes l6 are to be moved a distance corresponding to the length of the resistors, but the connection between the ends of the resistor 4| would not be absolutely necessary if the taps A and I were to be the limit of motion of the sliding brushes 16.

It will be observed that there are as many series of connections between taps as there are conductors 43 leading to the receiver, and that each series of connections joins resistors separated by a number of resistor divisions equaling the num ber of current-transmitting conductors and also connects to each adjacent pair of connected taps on one resistor the tap on the other resistor spaced intermediate the said pair of adjacent connected taps. With respect to the arrangement illustrated in which the brushes l8 are even with each other and the ends of the resistors 4| and 42 are also even, it will be observed that the cross connections from one resistor to the other join an adjacent connected pair of taps of one resistor to a tap of the other resistor which is displaced from either or the said pair of connected taps of one resistor one-half the distance between said pair of connected taps.

As the brushes 16 are moved along the resistors 4| and 42 the voltage distribution and polarities in the adjacent division of the resistors are progressively varied and cause .variation .in the distribution and polarities or the currents in the conductors 43 leading to the receiver. These variations in current distribution cause rotation oi the resultant magnetic field of the receiver and cause rotation of the pointer 3| as explained in connection with Fig. 1. However, inthe arrangement of Fig. 3, the voltages and currents vary through a complete cycle each time the brushes i6 traverse a third resistor length, and the action takes place smoothly and progressively from one end of the resistor to the other. Consequently, the receiver pointer 3| is rotated three times by passage of the brushes IS the entire length or the resistors 4| and 42. It will be understood that any desired greater number of revolutions may be produced by dividing the resistors 4| and 42 into a correspondingly greater number of parts or divisions and correspondingly increasing the number of taps and cross connections.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A transmitter for a telemeter system comprising a pair of resistors, a pair of brushes carried by a common support, one of said brushes being adapted to travel along one of said resistors and the other being adapted to travel along the other of said resistors, means for supplying current to said brushes, each of said resistors having a plurality of taps spaced therealong and dividing it into a plurality of divisions, the taps of one resistor being ofiset from those of the other, a plurality of conductors for transmitting current to a receiver, the number of said conductors being a fraction of the number of divisions of either resistor, series of connections between taps, there being as many series of connections as current-transmitting conductors, each series of connections joining taps on either one of said resistors separated by a number of resistor divisions equaling the number of current-transmitting conductors and also connecting to each adjacent pair of connected taps on one resistor the tap on the other resistor spaced intermediate the said pair of adjacent connected taps.

2. A transmitter for a telemeter system comprising a 'pair of resistors, a pair of brushes one adapted to travel along one of said resistors and the other adapted to travel along the other of said resistors, means for applying current to said brushes, a plurality of conductors connected to points spaced along one of said resistors for conveying current to a receiver, the sum of the spacings between said points being a fraction oi! the whole length or the resistor, both of said resistors being divided into divisions by taps spaced the same distances as said conductors, a series of cross-connections between said resistors for each of said conductors, each of said series of crossconnections connecting one of said conductors to taps on said resistors, the connected taps on either resistor being spaced by a number of resistor divisions equaling the number of conductors, and each tap on one resistor being connected to a tap of the other resistor displaced a distance one-half the length of spacing of the common connections on either resistor.

HAROLD T. FAUS. 

